The manufacture of power transmission members, to which this invention relates, utilizes a pair of racks and a mandrel to develop the tooth form in the periphery of an annular or tubular workpiece. The mandrel has the tooth form which is to be developed machined in an external peripheral working surface. A machine is provided for holding the mandrel and piece part and also includes tooth forming racks mounted on slides.
Tools for manufacturing tooth forms are shown in the patents to Pelphrey, U.S. Pat. No. 2,994,237, Miller, U.S. Pat. Nos. 3,827,280, 3,857,273, and 3,902,349, Anderson, U.S. Pat. No. 3,672,203 and Blue, U.S. Pat. No. 3,818,736. These patents show tooth forms having various characteristics for generating tooth forms in a cylindrical shaft member. The Miller U.S. Pat. No. 3,827,280 in particular discloses an initial section of sharp, file-like teeth adapted to grip and initiate rotation of a cylindrical workpiece followed by three sections of teeth adapted to generate a generally cycloidal tooth configuration which is then modified to the desired involute form by subsequent tooth sections. Another patent to Hildreth, U.S. Pat. No. 3,862,567 also shows a tool for manufacturing tooth forms which has selected teeth plated with copper, silver, gold or other suitable coating material to reduce tooth wear and fatigue. As can be seen in the aforementioned patents, the beginning or the leading portion of the tool has teeth which are deliberately altered in shape so that the rolling process will appropriately deform the metal in a gradual manner, thereby developing a final tooth shape which will be conjugate with the final tooth forms on the tool.
An early patent showing the rolling of a tooth form on a tubular element is U.S. Pat. No. 3,214,951 issued to McCardell. This shows a spline being rolled onto the outside of a tubular element. A later patent to Killop, U.S. Pat. No. 3,982,415 shows a splined mandrel and tool to specifically roll a power transmission member mounted directly on the mandrel. Here also, the teeth of the forming tool are shown having various shapes to gradually deform the metal so as to produce the desired tooth form both on the exterior of the power transmission member and on the interior thereof.
In using tools with tooth forms which have been shown in the prior art to spline tubular power transmission members, it was found that the wall thickness between the leading and trailing edge of a given tooth form on a power transmission member varies by as much as 50% and thus is extremely nonuniform in nature. Furthermore, a so-called wave or buckling effect in the workpiece generated ahead of the first toothed working section of the tool during the first 180.degree. of rotation has bee observed by Applicant to cause uneven flow of workpiece material and a resultant out-of-round condition. Improvements in the flow of workpiece material during the tooth-forming process are highly desirable and needed.
An object of the invention is to incorporate an initial section on the tool adapted to cooperate with the mandrel to minimize the wave effect in the workpiece during the first 180.degree. of rotation. Another object of the invention is therefore to reduce or eliminate the out-of-round condition caused by the wave effect.
Another object of the invention is to provide an improved tooth forming tool incorporating improved tooth generating means which improves the flow characteristics of the metal in the workpiece during the tooth generating process and develops a more uniform tooth element, especially improving uniformity in the wall thickness of the leading and trailing edges. Another object of the invention is to provide a tool for developing uniform tooth elements on both the external periphery and the internal periphery of the workpiece such as a power transmission member.
Another object of the invention is to provide an improved tool for pressure forming tooth elements in a cylindrical shell which enables the quantity production of tooth elements with improved quality. An object of the present invention is to provide an improved tooth forming tool of the indicated character incorporating improved means for generating teeth on tooth elements in a cylindrical tubular member whereby the strength and useful life of such tools is increased. A further object of the invention is to provide an improved tool for pressure forming tooth elements in a cylindrical tubular member which tool is economical and commercially feasible to manufacture, and is durable, efficient and reliable in operation.